175 



Austen (E. E.). Diptera : Tabanidae. (The Percy Sladen Trust 

 Expedition to the Indian Ocean in 1905, and 1907-1909). — Bull. 

 Entom. Res., Loridon, xi, no. 1, August 1920, pp. 43-45. 



The Tabanids brought back by the expedition include representatives 

 of four species, one being new. They are AegopJiagamyia terticeps^ 

 Aust., from Astove Island and Aldabra ; Bouvierella alluaudi, Giglio 

 Tos, and B. inornata, sp. n., from the Seychelles; and Tabanus 

 alhipedus, Bigot, from Aldabra, the Amirante, and other Isles. 



Lloyd (LI.). On the Reasons for the Variation in the Effects of 

 Formaldehyde as a Poison for House-flies. — Bull. Entom. Res., 

 London, xi, no. 1, August 1920, pp. 47-63. 



In a number of experiments with formaldehyde, the points considered 

 included the effect on its efficiency as a poison for Musca of 

 impurities in it, the humidity of the atmosphere, the strength of the 

 solution, and the addition of a bait. At the same time an attempt was 

 made to find the most effective mode of administration, and to 

 compare formaldehyde with other poisons. 



The results of these experiments are summarised as follows : — 

 The effective action of formaldehyde as a fly-poison depends on the 

 freedom of the exposed fluid from formic acid, and, to a less extent, 

 from methylamine. That used for fly-poison should therefore be 

 colourless and free from a fishy odour, and a weak alkali, in slight 

 excess, should be added to neutraHse any acid present or that will be 

 formed during exposure. The formula recommended is, 5-6 per cent, 

 of 40 per cent, formaldehyde, 50 per cent, of clear lime water, 2*5 per 

 cent, of sugar, and water to make 100. 



This should be exposed in a trap that will protect it from the air 

 and will prevent flies from falling into it. Formaldehyde, like any 

 other stomach-poison for flies, is most effective under dry conditions. 



Zetek (J.). Anopheles breeding among Water Lettuce. A New 

 Habitat. — fiidl. Entom. Res., London, xi, no. 1, August 1920, 

 pp. 73-75. 



This paper is a consideration of the possible danger to the Panama 

 Canal Zone that may be caused by the floating islands and other 

 masses of water lettuce {Pistia stratiotes) acting as a breeding place for 

 mosquitos. The water lettuce is the habitat of the very highly 

 specialised larvae of Taeniorhynclius {Mansonia), of which T. [M.], 

 titillans is the commonest member. But in 1918 Anopheles larvae 

 were also found in it. The habitat is favourable in many ways ; 

 the larvae are protected from the direct sun's rays, from larvicidal 

 fish, and to a large extent from predaceous insect larvae and wave 

 action. But the most important advantage is the exceptionally 

 favourable condition produced by the presence of the oxygen o-iven 

 off by the green lettuce. 



Another important aspect of the question is that the wind and current 

 detach portions of the floating vegetation, and carry it across deep 

 water to localities that the larvae would not otherwise reach. If 

 these floating islands have to be controlled — and it will depend on 

 the cumulative evidence gathered by the District Sanitary Inspectors- 



